module.exports = app => {
  const express = require('express');
  const mongoose = require('mongoose');

  mongoose.connect('mongodb://127.0.0.1:27017/homework', {
    useNewUrlParser: true,
    useUnifiedTopology: true
  });
  mongoose.connection.on('error', () => console.log('数据库连接失败'));
  mongoose.connection.on('open', () => console.log('数据库打开成功'));
  mongoose.connection.on('connected', () => console.error('数据库连接成功'));
}